1. Field of the Invention
The present invention relates to an autostereoscopic display system, and more specifically to a method of hardware based interdigitation for an autostereoscopic display system using component view-map tiles.
2. Description of the Related Art
The StereoGraphics SynthaGram™ is an autostereoscopic imaging product that utilizes an array of (typically slanted) lenticular elements on the display surface as shown in FIG. 1. U.S. Pat. No. 3,409,351 to Winnek describes the slant, or a process in which the lenticular axis is tipped at an angle to the vertical edge of the display. Special software in the StereoGraphics SynthaGram™ arranges multiple-view image information using an interdigitation mapping technique, such that someone viewing the display will see one of the left-eye views with their left eye and one of the right-eye views with their right eye. This results in a stereoscopic viewing experience without the need to use special glasses, mirrors, or other stereo selection devices used at the eye.
Typically, in the StereoGraphics SynthaGram™, approximately nine different source-view images are provided, each representing a different viewpoint to be integrated into the autostereoscopic scene. These source-view images may be from a photographic source or a computer graphics source, and may have been prepared previously, or in real-time (effectively at the same time that they are being displayed). The number of views may be greater or less than nine without loss of generality.
The StereoGraphics SynthaGram™ algorithm for interdigitation is called Interzig, and the two terms will used interchangeably throughout this disclosure. The interdigitation process takes subpixels (a subpixel is the red, green, or blue component of a single pixel) from all of the different source-view images, and arranges the sub-pixels in the resultant interdigitated image. For example, a subpixel from a particular source-view image might be copied to the Interzigged image, if that subpixel will appear under the portion of a micro-lens in the lenticular array corresponding to a particular viewing zone for the person viewing the image.
The interdigitation process performs the mapping of sub-pixels with an understanding of the optical display properties. These include the physical arrangement of the lenticular array (pitch, slant, offset) as well as the viewing distance between a viewer and the interdigitated image.
Finally, Interzigged subpixel data is passed to the actual subpixels in the display device and passed through a lenticular microlens array, resulting in an autostereoscopic viewing experience.
To speed up the Interzig process, the system may create a view-map. The view-map is encoded to indicate the specific source-view image used as the source for any given subpixel appearing in the final image, and an example of such a view-map is shown in FIG. 3. The interdigitation process thus takes the source view images, such as nine such source-view images, and maps them to a single view-map image, thereby speeding up the interdigitation process. Having a pre-calculated view-map saves the trouble and computation time of repeatedly calculating which source-view image should be used per any given subpixel in the final image. Once the source-view image is determined, by using the view-map such as that shown in FIG. 3 as a look-up table, the system can determine the intensity of a particular subpixel based on the color component value of a pixel in the appropriate image-map location belonging to the source-view image to which the view-map value points.
The view-map can be applied efficiently using different implementations including pixel masking, where the view-map spawns a set of binary masks that filter source-view images, and pixel, where fast per-pixel calculations are performed by referencing a view-map stored in the graphics device's texture.
Even with high-speed algorithms such as those described above, a performance penalty can result from a significantly large view-map. As described above, the view-map matches the full size of the final image being generated (and may take up an even larger segment of video memory). If the view-map and possibly the binary masks that the view-map generates could be smaller, the system would require less graphics memory, and considerable processing speed benefits could be realized. Processing speed benefits generally result from a decreased time to swap textures in and out of limited texture memory. Depending on the application, additional textures may be used for visual effects (surface patterns). The view-map texture competes for memory space with these other textures. For example, a final image created for a full screen size of 3840×2400 pixels requires an excessively large view-map sized at 4096×4096, if the graphics device has a power-of-2 size limitation.
The present design seeks to cure the problem of view map performance and time penalties to increase the throughput of the device and increase viewer enjoyment of the resultant autostereoscopic image. It would be advantageous to offer a design that employs a view-map in a more efficient manner within an autostereoscopic display system, particularly a design that offers benefits over those previously available.